1. Field of the Invention
The present invention relates to an image searching apparatus and an image searching method for searching content from a still image or a moving image.
2. Description of the Related Art
A way of capturing an image with changing a plurality of image capturing parameters (image capturing conditions) when images of a same object are captured is called “bracket capturing”. For example, in some cases, a user may continuously capture images using a reference exposure value selected when capturing a still image and a plurality of exposure values around the reference values. Then the user can select a desired image out of the captured images with the plurality of exposure values, and a failure, due to a mistake in selecting an image capturing parameter, can be prevented. This function is also useful when the user wants to keep the image capturing results with the plurality of different image capturing parameters.
Recently cases of capturing moving images with a digital single lens reflex camera are increasing, and compared with capturing images using a conventional digital video camera, various expressions using various interchangeable lenses are applied to moving images. Therefore in future, the demand for “bracketed moving images” which capture moving images by bracket capturing will probably increase.
Bracket capturing for moving images means recording and capturing each frame of a moving image using a plurality of image capturing parameters (image capturing conditions), and in this description a moving image captured like this is defined as a “bracketed moving image”.
FIG. 6 shows an example of a bracketed moving image and a normal moving image. The parameter to be changed during bracket capturing is not limited to the above mentioned exposure, but could be various parameters, including focus, ISO sensitivity, white balance, angle of view and shutter speed. If a double lens camera, which can capture a 3-D image, is used to capture an image for the left eye and an image for the right eye, the respective view point position of the image for the left eye and the image for the right eye correspond to the image capturing parameters.
The upper part of FIG. 6 shows an example of a bracketed image when focus is changed as a bracket parameter. The frames indicated by a reference number 101 captured with focus A are in a state of focusing on a position of a person out of objects, and the frames indicated by a reference number 102 captured with focus B are in a state of focusing on a position of a vehicle. In the case of the frames 103 of the ordinary moving image shown at the lower part of FIG. 6, on the other hand, the image capturing parameter is one fixed value.
In the example in FIG. 6, when this bracketed moving image is reproduced, the user can select and regenerate a desirable image out of the frames 101 and frames 102. In concrete terms, the frames 101 are reproduced if the state of focusing on the position of a person is desirable, and the frames 102 are reproduced if the state of focusing on the position of a vehicle is desirable. It is also possible to switch the frames 101 and frames 102 during reproduction.
In the case of a bracketed image, an image of a similar scene or content is captured for a plurality of times, regardless whether it is a still image or a moving image, so data volume and a number of frames per object increase more than a normal moving image. In the case of the example of the bracketed moving image in FIG. 6, two types of focus (focus A and focus B) are used for the bracketed moving image, so a number of frames that is double a normal moving image is required, while a normal moving image is one moving image stream constituted by continuous frames.
When a desired image is retrieved from many images including a bracketed image, a good bit of waste is generated if all the data and frames simply become the searching target. For example, in the case of a bracketed image having different focus areas (focus A and focus B), as shown in FIG. 6, it takes search time double that of a normal moving image, even if the content of the image capturing target is similar in the frame group with focus A and the frame group with focus B. In the case of performing search processing for searching a desired image based on image recognition technology, even if the search target is a still image, the time required for search processing becomes long, if the number of still images is high. If the search target is a moving image, longer time is required for the search processing than the case of a search target that is a still image.
To retrieve a bracketed image, it has been proposed to select image capturing conditions and display an image group matching the image capturing conditions as the search result, so that the desired image can be easily retrieved (e.g. Japanese Patent Application Laid-Open No. 2008-252682).
Japanese Patent Application Laid-Open No. 2008-182662 discloses only “one frame display image”, out of an image file consisting of “attribute information”, a “main image” data, an “index display thumbnail image” data and “one frame display image” data.
Japanese Patent Application Laid-Open No. 2005-167469 discloses that if a thumbnail image, to which an identifier information for bracket capturing is attached, exists, a representative thumbnail image (e.g. thumbnail image having a central exposure value) is selected, and a list of thumbnail images is displayed.
According to the technology disclosed in Japanese Patent Application Laid-Open No. 2008-252682, if the image capturing conditions are attached to an image in such a format as meta data, this attached information is retrieved from all the images. Since a bracketed image is the target, it is effective to retrieve the image using the image capturing conditions.
However when all images are the search target, search time increases in proportion to the number of bracket parameters. Also recently it is common to retrieve content based on image recognition technology (e.g. searching an image which is “reddish” and “Mr. A” is captured), but the method of using image capturing conditions of prior art cannot be used for searching by content.
In the case of the technology according to Japanese Patent Application Laid-Open No. 2008-182662, a bracketed image is not assumed, so the search targets becomes “one frame display image” data of all bracketed images. Japanese Patent Application Laid-Open No. 2005-167469 is not based on the assumption that search processing is performed for searching a desired image using image recognition technology.